Relationship between colour and brown pigment concentration in orange juices subjected to storage temperature abuse

The browning index of orange juices which had been subjected to storage temperature abuse (55°C for up to 40.5 hr) was highly correlated with the CIE tristimulus values as measured on a Neotec Du-Color Colour Difference Meter. The correlation coefficients and the multiple regression equation have been calculated. When the tristimulus values were converted to USDA colour scores, the values obtained were not in the same range as the USDA plastic standards for orange juice. The level of correlation between the colour scores and the browning index was too low to be useful for prediction purposes. When the tristimulus values were converted to Hunter's citrus red and citrus yellow parameters, a significant correlation was found between these parameters and the browning index. However, the level of variation explained by the correlation was again too low to be useful for prediction purposes.     

Testing the self as a control system: Theoretical and methodological issues

This report describes an evolution of research methodology for adducing evidence regarding whether the self functions as a control system. While there has been a great number of studies in the literature on personality and social psychology aimed at demonstrating that behavior of many kinds can be affected by focusing attention upon the subject's self-concept, or by challenging or threatening it, little attention has been given to the question of why this would be so. A proposed explanation would be that the self functions as a control system. Testing this hypothesis has entailed development of a methodological approach in which control action occurs predictably rather than having a statistical probability. This has required defining a model and testing it by predictions rather than attempting to isolate underlying variables with multivariate techniques.     

BOOK REVIEWS

HEAT TRANSFER AND FOOD PRODUCTS. Bengt Hallström, Christina Skjölderbrand and Christian Trägårdh. Elsevier Applied Science Publishers, London and New York. 1988. pp. xiv + 263.
FLAVOUR ENCAPSULATION. (S. J. Risch and G. A. Reineccius, eds.) ACS Symposium Series 370, ACS, Washington D.C., 1988, 202 pp. $54.95 U.S. and Canada $65.95 Elsewhere.
POSTHARVEST PHYSIOLOGY OF VEGETABLES. (J. Weichmann, ed.) Marcel Dekker, New York and Basel. 1987. 597 pp. $150 U.S. and Canada, $180 all other countries.
PROGRESS AND TRENDS IN RHEOLOGY II. (editors H. Giesekus, M. F. Hibberd, P. Mitschka, P. Riha and J. Sestak, eds.) Steinkopf-Verlag, Darmstadt, Springer-Verlag, New York. 502 pp. DM 280.
HPLC IN FOOD ANALYSIS. (R. Macrae, ed.) Academic Press, London, 493 pp. $77.50 U.S. £55 elsewhere.
WATER ACTIVITY: THEORY AND APPLICATIONS TO FOODS. (L. B. Rockland and L. R. Beuchat, eds.) Marcel Dekker, New York 1987. ISBN 0-8247-7759-X; 404 pp.; $59.75 in the U.S. and Canada; $71.50 elsewhere.
GUMS AND STABILISERS FOR THE FOOD INDUSTRY. (G. O. Phillips, D. J. Wedlock and P. A. Williams) IRL Press, Oxford and Washington, 560 pp. £50 U.S. $100.
SAVOURY COATINGS. (D. B. Fuller and R. T. Parry, eds.) Elsevier Applied Science Publishers, New York. 130 pp., 1988. $47.00.
TOTAL QUALITY ASSURANCE FOR THE FOOD INDUSTRIES. W. A. Gould and R. W. Gould. CTI Publications, Baltimore. 1988. 394 pp. $50 in the U.S. $65 overseas.     

A capacitance study of the silver(I)/copper displacement reaction

Metal displacement (cementation) reactions are usually diffusion controlled and conform to first order kinetics. When a displacement reaction is carried out in a batch reactor, positive deviations from a first order rate plot are commonly observed once the deposit becomes sufficiently thick. It has been suggested that these rate enhancements are the result of changes in deposit structure resulting in increases in surface area. Another theory argues that the rate enhancements are due to turbulence associated with increasing roughness of the deposit. In this paper, an attempt is made to discriminate between these two possibilities by measuring the capacitance of a copper electrode immersed in a silver(I) solution. It was found that no anomalous capacitance changes were observed corresponding to the region in which rate increases were observed. This suggests that turbulence effects, rather than area effects, are responsible for the increased reaction rate. Capacitance measurements were also conducted for the reaction between silver(I) and copper in the presence of cyanide which caused the silver to deposit in a thin uniform layer on the copper surface, thus blocking the displacement reaction. It was found that the capacitance changed very little with time under these circumstances.     

Saturation Factors for Calcium Hydroxide and Calcium Sulfates in Fresh Portland Cement Pastes

Aqueous extracts from five cement pastes at w/c = 0.5 were analyzed for Ca²⁺, SO^2–₄, Na⁺, and K⁺. Degrees of saturation with respect to portlandite, gypsum, and syngenite were determined at ages from 6 min to 3 h, taking into account ionic association effects. Portlandite saturation is usually attained within a few minutes of mixing, but rates of saturation vary. The maximum degree of saturation is 2 to 3 times the equilibrium value and is attained within 2 h. Initial super-saturation with respect to gypsum, and in some cases syngenite, occurs at very early ages and declines to the saturation level within 12 min. Results are interpreted by use of a solution-precipitation model for cement hydration. The calculated critical size of portlandite nuclei at early ages is ∼0.1 μm. Slow growth of portlandite nuclei suggests a surface poisoning phenomenon.     

Estimating suspended sediment concentrations from spectral reflectance data

Abstract

A method for estimating sediment concentrations at different depths in coastal waters from measured spectral reflectance above the sea is proposed. The water backscattering coefficient is obtained by integrating a scattering cross section derived from Mie theory over a Junge type particle-size distribution. The results for turbid water, near an arid coast, with vertical mixing, shows a maximum of particle concentration in the middle layer, while the same method applied to reflectance data for ‘blue’ water, gives a relative concentration of sediment that gradually increases with depth.